Journal ArticleDOI
Kinetic theories for granular flow: inelastic particles in Couette flow and slightly inelastic particles in a general flowfield
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In this paper, the authors studied the flow of an idealized granular material consisting of uniform smooth, but nelastic, spherical particles using statistical methods analogous to those used in the kinetic theory of gases.Abstract:
The flow of an idealized granular material consisting of uniform smooth, but nelastic, spherical particles is studied using statistical methods analogous to those used in the kinetic theory of gases. Two theories are developed: one for the Couette flow of particles having arbitrary coefficients of restitution (inelastic particles) and a second for the general flow of particles with coefficients of restitution near 1 (slightly inelastic particles). The study of inelastic particles in Couette flow follows the method of Savage & Jeffrey (1981) and uses an ad hoc distribution function to describe the collisions between particles. The results of this first analysis are compared with other theories of granular flow, with the Chapman-Enskog dense-gas theory, and with experiments. The theory agrees moderately well with experimental data and it is found that the asymptotic analysis of Jenkins & Savage (1983), which was developed for slightly inelastic particles, surprisingly gives results similar to the first theory even for highly inelastic particles. Therefore the ‘nearly elastic’ approximation is pursued as a second theory using an approach that is closer to the established methods of Chapman-Enskog gas theory. The new approach which determines the collisional distribution functions by a rational approximation scheme, is applicable to general flowfields, not just simple shear. It incorporates kinetic as well as collisional contributions to the constitutive equations for stress and energy flux and is thus appropriate for dilute as well as dense concentrations of solids. When the collisional contributions are dominant, it predicts stresses similar to the first analysis for the simple shear case.read more
Citations
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Journal ArticleDOI
Hydrodynamic modelling of binary mixture in a gas bubbling fluidized bed using the kinetic theory of granular flow
TL;DR: In this paper, a multi-fluid Eularian CFD model with closure relationships according to the kinetic theory of granular flow has been applied to study the motions of particles in the gas bubbling fluidized bed with the binary mixtures.
Journal ArticleDOI
Computational fluid dynamics (CFD) modeling of spouted bed: Influence of frictional stress, maximum packing limit and coefficient of restitution of particles
TL;DR: In this article, the influence of the frictional stress, maximum packing limit and coefficient of restitution of particles on the spouted bed hydrodynamics has been investigated using two-fluid simulation of spouted beds.
Journal ArticleDOI
Eulerian simulations of bubbling behaviour in gas-solid fluidised beds
van Bgm Berend Wachem,van Bgm Berend Wachem,JC Jaap Schouten,Rajamani Krishna,van den Cm Bleek +4 more
TL;DR: In this article, a CFD model for a free bubbling fluidised bed was implemented in the commercial code CFX of AEA Technology, which is based on a two fluid model including the kinetic theory of granular flow.
Journal ArticleDOI
Overview of Computational Fluid Dynamics Simulation of Reactor-Scale Biomass Pyrolysis
Qingang Xiong,Yang Yang,Fei Xu,Yaoyu Pan,Jingchao Zhang,Kun Hong,Giulio Lorenzini,Shurong Wang +7 more
TL;DR: In this paper, the state-of-the-art progress in computational fluid dynamics (CFD) modeling of reactor-scale biomass pyrolysis was summarized and discussed, and the theoretical basis and practical applications of three main CFD modeling approaches, i.e., porous media model, multifluid model, and discrete particle model, were presented.
Journal ArticleDOI
Fluid dynamic simulation of O3 decomposition in a bubbling fluidized bed
TL;DR: In this paper, a simulation of premixed ozone (O 3 ) decomposition in a bubbling fluidized bed using the multiphase CFD code MFIX was conducted. And the grid-independent results were in very good agreement with reported experimental data on total conversion over a range of fluidization velocities and initial bed heights.
References
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Journal ArticleDOI
Equation of State for Nonattracting Rigid Spheres
TL;DR: In this paper, a new equation of state for rigid spheres has been developed from an analysis of the reduced virial series, which possesses superior ability to describe rigid-sphere behavior compared with existing equations.
Journal ArticleDOI
Experiments on a Gravity-Free Dispersion of Large Solid Spheres in a Newtonian Fluid under Shear
TL;DR: In this article, a large number of spherical grains of diameter D = 0.13 cm were sheared in Newtonian fluids of varying viscosity (water and a glycerine-water-alcohol mixture) in the annular space between two concentric drums.
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